1. Field of the Invention
The present invention relates to quick-release clamping locks of the knuckle action or knee lever type, and, more particularly, to a knee lever lock of the type which is usable in connection with automotive air filters, for the clamping attachment of a filter cover to a filter housing.
2. Description of the Prior Art
Quick release knee lever locks using a knee lever and an attached hook member which, through the pivoting action of the knee lever, is pulled into clamping engagement, have become widely accepted as clamping locks for air intake filters, particularly for carburetor-mounted shallow air intake filters, where a substantially flat filter cover of large diameter is clamped against the rim of a pan-shaped filter housing. Usually, four or five of these knee lever locks are arranged at regular intervals on the periphery of the filter housing.
Known knee lever locks of the type under consideration commonly consist of two principal parts: a curved, resiliently extendable hook member and a knee lever which is pivotably attached to the filter housing. The hook extremity of the hook member engages a bead or groove on the periphery of the filter cover, and its opposite extremity is pivotably attached to the knee lever. This pivot attachment and the fixed pivot of the knee lever on the filter housing are so arranged that, when the knee lever is pivoted downwardly against the filter housing wall, it moves the hook member pivot beyond the dead center point with respect to the force line which links the hook extremity and the fixed pivot. In this position, the pull of the hook member urges the knee lever against the filter housing, thereby holding the lock in its closed position. The curved hook member, acting as a spring, thus produces a reliable clamping action, unaffected by vibration. This type of knee lever lock is simple and inexpensive. It is easy to operate, and, in most cases, lends itself well for mass production.
One such knee lever lock is disclosed in German Gebrauchsmuster (Utility Model) No. 1,661,181. This lock is used to clamp an angularly resettable dome-shaped filter cover against a pot-shaped filter housing. The disclosed lock assembly consists of a curved hook member whose hook extremity is formed by the yoke of a U-shaped wire part and whose inwardly bent extremities form pivot trunnions. The latter engage matching pivot holes in a knee lever in the form of a sheet metal stamping. The fixed pivot for the knee lever is provided as part of a pivot support member. This member is likewise a sheet metal stamping of U-shaped outline which is spot-welded to the wall of the filter housing. The highly stressed spot weld represents a comparatively expensive operation, requiring special tooling and equipment. Furthermore, such a spot welding operation represents difficulties in terms of quality control, under mass production conditions.
Another version of a prior art knee lever lock is suggested in German Gebrauchsmuster (Utility Model) No. 1,769,842. This unit is designed for use on a filter housing of injection-molded plastic for an oil bath air cleaner, suggesting the arrangement of the fixed pivot supports for the knee levers in the form of integrally molded radial extensions on the housing wall, near the rim of the latter. Obviously, this approach is not usable in connection with a filter housing of sheet metal.
A further prior art knee lever lock is disclosed in German Gebrauchsmuster (Utility Model) No. 73 07 369. This disclosure suggests a knee lever lock on a filter housing of sheet metal, where the previously required pivot support member has been eliminated, and the pivot apertures for the knee lever are formed in the wall of the filter housing itself. But, because of the necessity for the fixed pivot point to be located radially outside the force line between the clamping point of the hook member and its pivot point on the knee lever in the clamped position, it becomes necessary to either extend the wall of the filter housing radially outwardly beyond its normal rim diameter, in the form of lug-like pivot extensions of the housing wall, or to provide appropriate inward depressions in the wall of the filter housing below the knee lever pivot point, for a pivoting movement of the knee lever beyond the dead-center position of the hook member.
While the arrangement of lug-like extensions of the housing wall is costly in terms of material requirements as well as tooling, the arrangement of depressions in the filter housing wall is not only similarly costly, but is also in conflict with the need for a cylindrical filter housing with optimal air flow conditions. On the other hand, the additional space which is required for this type of knee lever lock is frequently not available.